Vigorous or Moderate Physical Activity in the Prevention of Cardiovascular Disease?

Physical activity clearly is associated with lower risk of cardiovascular disease. What is less clear are the kinds and intensity of physical activity associated with lower risk. This is important to clarify in llght of a recent physical activity recommendation that calls for at least 30 minutes of moderate-intensity physical activity (e.g., brisk walking at 3-4 mph), mos! days of the week. This contrasts with previous recommendations that advocated vigorous-intensity exercise (e.g., jogging or running), for at least 20 minutes continuously, 3 times a week. A major difference is the present emphasis on moderate, instead of vigorous, activity. This concession was made partly to encourage physical activity among those sedentary since lhe previous, more difficult prescription was believed to pose a barrier. To assess whether vigorous or moderate physical activity is needed to decrease lhe risk of cardiovascular disease, we can evaluate the data from studies examining two different kinds of outcomes. First, we can look at data from studies investigating lhe effect of vigorous or moderate physical activity on risk factors for cardiovascular disease, such as blood pressure, lipid profile, or insulin sensitlvity. BecaCJse these parameters can change over a relatively short period of time, on lhe order of weeks to months, such studies can be conducted over the short term. The assumption ls that improvements in these short term risk factors will ullimately translate to a benefit for cardiovascular disease itself. Second, we can examine data from studies investigating the assoclation of vigorous or moderate physical activity with risk of cardiovascular disease itself. Such studies take far longer to carry out, on the arder of years, since cardiovascular disease takes a long time to develop. However, the second group of studies provides more direct evidence. The data from the first group of studies clearly shows that even moderate physlcal activity can beneflt risk factors for cardiovascular disease. However, the data from lhe second group of studies have been less consistent. There are severa! methodologic issues that may explain lhe inconsistencies observed; these will be discussed in this lecture.

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